1. Field of the Invention
The present invention relates to an examination apparatus for acquiring three-dimensional images of a specimen.
This application is based on Japanese Patent Application No. 2006-001670, the content of which is incorporated herein by reference.
2. Description of Related Art
In a known technology in the related art, light-emitting areas, in which light is emitted from light-emitting points located inside a specimen such as a small laboratory animal and appears on the surface of the specimen, form a surface image, which is imaged from a plurality of directions, and the light-emitting areas on the surface of the specimen, which is represented three-dimensionally, are superimposed to be three-dimensionally displayed (for example, see US Patent Application No. 2004/0021771 (hereinafter referred to as Document 1)).
However, with the technology in Document 1, it is not possible to observe an image of the light-emitting sites inside the specimen.
A known apparatus for observing an image of the light-emitting sites inside a specimen is a confocal fluorescence microscope. Because a confocal fluorescence microscope images only light passing through a confocal pinhole, which is located at a conjugate position with respect to a focal point of an objective lens, it is possible to acquire an image of the light-emitting sites inside the specimen with extremely high resolution in the optical-axis direction. Then, based on a plurality of images acquired by shifting the focal point in the optical-axis direction, it is possible, in principle, to form a three-dimensional image of the light-emitting sites inside the specimen.
In practice, however, because the specimen, such as a small laboratory animal, is formed of scattering substances, the light emitted from the light-emitting sites located deep within the specimen is scattered before it reaches the specimen surface. Therefore, when observing sites deep inside the specimen, such as a small laboratory animal, from outside using a confocal fluorescence microscope apparatus, the light from the light-emitting sites is scattered, which causes the amount of light passing through the confocal pinhole to be reduced. This causes a problem in that, in some cases, it is almost impossible to form an image.
Conversely, when the pinhole diameter is increased, because the depth of field is increased, it is possible to make a lot of the light from the vicinity of the light-emitting sites inside the specimen pass through the pinhole, and it is thus possible to acquire a bright image.
However, when the depth of field is increased, an image which is in-focus at the focal point and focus-shifted images at positions shifted towards both sides in the optical-axis direction of the focal point are superimposed and acquired by an image-acquisition device, and it is thus not possible to acquire a clear image. Therefore, even though a plurality of unclear images acquired by shifting the focal position in the optical-axis direction are used, there is a problem in that it is not possible to acquire a clear three-dimensional image.